Circuit closing devices



United States Patent CIRCUIT CLOSING DEVICES Morton A. Levine, Beverly, and Stanley W. Davis, Jr.,

Canton, Mass., assignors to the United States of America as represented by the Secretary of the Air Force Application July 12, 1957, Serial No. 671,679

4 Claims. (Cl. 200-87)' (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to us of any royalty thereon.

The present invention relates generally to circuit closing devices and, as illustrated herein, relates more particularly to rapid closing, high-current electrical switches.

The switch embodying the present invention is designed to switch larger currents at higher speeds than have heretofore been possible. The present circuit closing device has a low inductance. The illustrated form of switch reduces multiple closing. Rapid closing of the switch reduces heating and pitting of the contact surfaces. To produce this rapid action, the contact surfaces are so related that the current flow in the circuit is such that a force is produced which causes the contact members to be attracted toward each other.

The drawings illustrate a preferred embodiment of the present invention wherein the contact elements of the switch utilize the current flowing therethrough to move the contact elements into and to maintain them in circuit closed position. Preferably, one of the contact memhers is flexible and the circuit is closed by moving the flexible contact into circuit closing engagement with another contact member. The circuit closing movement may be initiated by moving one of the contact members either mechanically or by the use of an ionizing trigger toward the other contact member. When a spark is .made to jump from one contact to the other, current flows in the circuit and a force exists between the contact members which is proportional to the square of the current and inductance increases in the direction of movement of the movable contact. Thus, in the present device, the flow of current through the switch helps to close the switch. Initial current flow through the switch is low but increases at a very high rate as the contact elements approach circuit closed position. The fast closing action reduces heating and pitting of the contact surfaces and multiple closing or jitter is substantially eliminated.

The embodiment shown in the drawings represents a preferred form of the present invention but it is apparent that changes therein may be made therein without departing from the principle of the present invention.

In the drawings:

Fig. 1 is a view in section of a preferred embodiment of the present invention;

Fig. 2 is a detail view, in section showing the parts in circuit closed position; and

Fig. 3 is a view in end elevation of the breaker.

Fig. 1 of the drawings illustrates a sectional view of a mechanical circuit closing switch. The switch comprises a pair of outer plates 12, 14 formed of suitable rigid material, such as brass, which support and protect the switch elements. The plates 12 and 14 are mounted on insulating plates 16 and 18 which are recessed to receive the switch elements as will later be described and are formed of suitable electric insulating plastic sheet 34, and the sets of flexible conductors material such as tetrafluoroethylene manufactured under the trademark Teflon.

The conducting elements of the switch comprise a twopiece element formed of two plates 20 and 22 formed of electrical conducting material which are insulated from each other by a sheet 24 of suitable insulating material. Preferably, the sheet 24 is formed of a flexible plastic film such as polyethylene terephthalate resin, having high thermal stability and having outstanding dielectric strength. One end of the conducting plate 22 is cut away to provide a recess 26 into which a portion of the insulating strip 24 extends. The outer end positions of the conducting plates 20, 22 are also cut away, as shown in Fig. 1, to correspond with similar end portions on a second conducting plate 28 which is formed of one piece of conductive material such as copper.

The conducting plates 20, 22 and 28 are separated from each other by suitable sheets 30 formed of dielectric material such as polyethylene terephthalate. The insulating sheet or film 24 which separates the plates 20, 22 extends into the recess 26 and overlies a flexible conductor 32 which is formed of relatively narrow and very thin strips of copper. These strips as illustrated, are about 2% inches in length, /2 inch wide and .010 inch thick. A suitable number of such strips are stacked to form the conductor 32 and the number of strips may be varied depending upon the current which the switch 10 is designed to carry. A flexible sheet 34 of insulating material underlays the flexible conductor 32. Below the insulating sheet 34 is another stack 36 of copper sheets which, as illustrated, are each approximately 2% inches long, 2 inches wide and 0.10 inch thick. The insulating sheet 34 and the conducting stack 36 are interposed between the plate 20 and the plastic insulating sheet 30, as shown best in Fig. 2.

The flexible conductor 32 extends beyond the left hand end of the insulating sheet 24, a distance sufiicient to permit substantial contact between the flexible conductor 32 and the conductor plate 22. The insulating sheet 34 and the copper sheet 36 extend beyond the end of the conductor 32 but terminate short of the left hand end of the recess 26. The copper sheet 36 covers substantially all of the exposed area of the plastic insulating sheet 30 and acts as a spark arrester to prevent damage to the insulating sheet 30. The insulating sheets 30 and 32, 36 are maintained in position by clamping portions of said members between the plates 20, 22 and 28 by suitable clamping bolts 40 which extend through the cover plates 12, 14 and the insulator plates 16, 18. As best shown in Fig. 3, the bolts 40 are spaced from the conducting elements and are insulated therefrom by the insulating blocks or plates 16, 18.

The construction described above is designed to switch higher currents in shorter times than were heretofore possible. The switch is designed to have a low inductance and is able to carry very high currents. Because one of the contact members is flexible, multiple closing or jitter and contact erosion, which are troublesome in mechanical switches of prior known construction, are reduced to a minimum.

In the present construction, terminals 42 and 44 are formed as a part of or are secured to the conducting members 22, 28 and are connected to a suitable source of electric power. The terminals 42', 44' are attached to conducting member 20 and the opposite end of conducting member 28 respectively and may be electrically connected to a suitable load. The current flow through the switch is from the source of power to the plate 22 through the flexible contact 32 through the block 20 to the terminal member 42'. The current then flows through the load and back to the terminal 44' and through the block 28 to the source of power.

The present device is designed to malre use of the electrical principle that conductors in which current is flowing in opposite directions are normally repel: J. from each other. Thus the flow of current through the switch assists the closing of the switch and eliminates substantially entirely any jitter or chattering of the contacting member thus reducing contact erosion due to arcing.

The circuit through the present switch may be closed electrically or mechanically as by movement of rod formed of suitable dielectric material. A spark is caused to jump from the block 22 to the flexible lead or contact 32 thus initiating a flow of current through the switch 10. The current flow is initiated either by an ionizing current or by mechanical movement of the flexible con tact 32 toward the plate 22. After current begins to flow from the block 22 to the flexible contact 32, the flexible contact 32 is forced toward the plate 22 and resistance to current flow is reduced. hus the current flow is increased and the force exerted on the flexible contact 32 is proportional to the current squared. This force serves rapidly to close the switch and to made a firm contact.

The characteristics of the present switch are such as will permit use in high current pulse circuits since the switch permits lower inductance leads and thus higher currents in pulse circuits. The high speed closing of the switch under high current conditions makes it a suitable and desirable replacement for more costly gas trigger tubes such as ignitrons.

Although the present invention has been described with particular reference to a preferred embodiment thereof it is apparent that the invention is not limited thereto but that various changes may be made within the scope of the appended claims.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is:

l. A switching device for high speed control of large currents comprising, a pair of current conducting members in parallel relationship to each other, one of said conducting members for carrying current from a source to a load, the other conducting member carrying the return current from the load to the source, the first named conducting member being divided into two portions each longitudinally displaced from the other, a flexible contactor in permanent contact with one of the portions of the divided conducting member, and means for flexing said contactor into engagement with the other portion of the divided conductor member electrically connecting both portions and allowing current to flow therethrough, the return current flowing in the opposite direction through the undivided conducting member.

2. The switching device described in claim 1 wherein a flexible strip of non-conducting material is disposed between the longitudinally displaced portions of the divided conducting member, said non-conducting strip extending into a space between said pair of current conducting members, part of said flexible contactor being adjacent to the extended portion of said non-conducting strip leaving an exposed part of said flexible contactor to engage the other portion of the divided conductor member.

3. Tl e switching device described in claim 1 wherein the means for flexing said contactor into engagement with the other portion of the divided conducting member includes a rod of dielectric material constructed and arranged to slide in an aperture in the undivided conducting member, said rod contacting a surface of the contactor and urging it into engagement with the other portion of said conducting member.

4. In a circuit closing device for controlling the passage of high current, a first conducting member and a second conducting member in parallel spaced relation to each other, the first conducting member being longitudinally separated into a line portion and a load portion having a non-conducting area therebetween, a flexible insulating material disposed in said non-conducting area and extending into a space between said first and second conducting members, a flexible contact member adjacent to the extended portion of said insulating material and including an exposed outer end, said contact member having an inner exposed end in direct contact with the load portion of said first conducting member, means for urging said contact member including its exposed outer end into electrical contact with the line portion of the first conducting member, to cause current to flow therefrom through the contact member to the load portion, the circuit completing current returning from the load through said second conducting member being in the opposite direction creating a repelling force which acts to urge the flexible contact member more tightly against the line portion of said first conducting member preventing multiple closing of the device.

References in the file of this patent UNZTED STATES PATENTS 1,806,322 Walle May 19, 1931 2,732,468 Curtis et al. Jan. 24, 1956 2,854,543 Wilson Sept. 30, 1958 FOREIGN PATENTS 896,543 France May 2, 1944 672,681 Germany Mar. 8, 1939 

